Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
SERVICE PROVIDING SYSTEM, OUTSOURCING BUSINESS DEVICE,
SERVICE PROVIDING METHOD, AND PROGRAM
Technical field:
The present invention relates to a service providing system, an
outsourcer apparatus, a service providing method, and a program, and more
particularly to a service providing system, an outsourcer apparatus, a service
providing method, and a program for allowing an entrustor to transfer a
service for the members of the entrustor to an outsourcer.
Background art:
It is more or less practiced for an entrustor having a plurality of
members to transfer a service for the members to an outsourcer. In this
case, the outsourcer confirms that the user, who requests a service, is a
member of the entrustor and thereafter provides the service for the members
to the user. Therefore, though the outsourcer does not need to authenticate
individual users, but is required to confirm that each user is a member of the
entrustor.
According to outsourcing systems of the background art, it is necessary
for the entrustor to give the outsourcer member information that the entrustor
has in order for the outsourcer to confirm whether a user is a member of the
entrustor or not.
JA-P No. 2004-38494 discloses a contents providing system which
makes it possible for an outsourcer to identify a user as an entrustor's
member without the need for the entrustor to give its member information to
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the outsourcer.
When the user apparatus is to receive the service from the outsourcer
apparatus (contents distribution server), the contents providing system
operates as follows:
First, the user apparatus communicates with the entrustor's apparatus
(user information management server) and is authenticated by the entrustor
apparatus. Only when the authenticating process is completed normally, the
user apparatus receives the service from the outsourcer apparatus via the
entrustor apparatus.
In recent years, there has also been known a group signature system
based on a group signature scheme (see Non-patent document 1).
According to the group signature system, a member of a group can
create a signature indicating that the member belongs to the group. When
the signature is authenticated, the fact that the signature has been generated
by the member of the group can be confirmed, but the information about the
creator of the signature is not known. However, an entity with a special
authority can identify the creator of the signature.
Patent document 1: JA-P No. 2004-38494
Non-patent document 1: G. Ateniese, J. Camenisch, M. Joye, G.
Tsudik, "A Practical and Provable Secure Coalition-Resistant Group
Signature Scheme" (Advances in Cryptology - CRYPTO 2000, LNCS 1880,
pp. 255 - 270, Springer-Verlag, 2000)
Disclosure of the invention:
Problems to be solved by the invention:
According to the outsourcing system of the background art, the
entrustor needs to give the outsourcer the member information which the
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entrustor has in order for the outsourcer to confirm whether a user is a
member of the entrustor or not.
Consequently, the member information of the entrustor may possibly
leak from the outsourcer. For preventing the member information from
leaking, the outsourcer is required to manage the member information
strictly. As a result, the cost required to manage the member information is
high.
According to the contents providing system disclosed in JA-P No.
2004-38494, the user needs to communicate with the entrustor each time the
user requests the service. Therefore, the number of communication
sessions tends to increase.
Non-patent document 1 is silent as to a system including an entrustor
apparatus and an outsourcer apparatus.
It is an object of the present invention to provide a service providing
system, an outsourcer apparatus, a service providing method, and a program
for allowing an entrustor to transfer a service for the members of the
entrustor to an outsourcer without the need for giving member information to
the outsourcer.
Another object of the present invention is to provide a service providing
system, an outsourcer apparatus, a service providing method, and a program
for not requiring a user to communicate with an entrustor when the user
receives a service from the entrustor.
Means for solving the problems:
To achieve the above objects, a service providing system according to
the present invention includes a user apparatus, an entrustor apparatus for
registering the user apparatus as a member for receiving a predetermined
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service when a registration request for enrolling the user apparatus as the
member is received from the user apparatus, and an outsourcer apparatus
for providing the predetermined service to the member which has requested
the predetermined service on behalf of the entrustor apparatus, the
arrangement being such that when the outsourcer apparatus is requested to
provide the predetermined service by the user apparatus, the outsourcer
apparatus authenticates whether the user apparatus is the member or not
according to a group signature scheme, wherein the entrustor apparatus
comprises a group key generator for generating public information, a
member registration key, and an open key for use in the group signature
scheme, a public information provider for providing the public information
generated by the group key generator to the outsourcer apparatus, a
signature key generator for generating a signature key corresponding to the
user apparatus using the public information and the member registration key,
in response to the registration request from the user apparatus, and a
signature information provider for providing the signature key generated by
the signature key generator and the public information to the user apparatus,
the user apparatus comprises a group signature generator for generating
group signature data using the signature key and the public information
provided by the signature information provider and a request for the
predetermined service, and a group signature data provider for providing the
group signature data generated by the group signature generator and the
request for the predetermined service to the outsourcer apparatus, and the
outsourcer apparatus comprises an authenticator for authenticating whether
the group signature data provided by the group signature data provider is
legitimate or not using the public information provided by the public
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information provider, and a service provider for providing the predetermined
service to the user apparatus in response to the request for the
predetermined service if the authenticator judges that the group signature
data is legitimate.
A service providing method according to the present invention is to be
carried out by a service providing system including a user apparatus, an
entrustor apparatus for registering the user apparatus as a member for
receiving a predetermined service when a registration request for enrolling
the user apparatus as the member is received from the user apparatus, and
an outsourcer apparatus for providing the predetermined service to the
member which has requested the predetermined service on behalf of the
entrustor apparatus, the arrangement being such that when the outsourcer
apparatus is requested to provide the predetermined service by the user
apparatus, the outsourcer apparatus authenticates whether the user
apparatus is the member or not according to a group signature scheme, the
service providing method comprising a group key generating step in which
the entrustor apparatus generates public information, a member registration
key, and an open key for use in the group signature scheme, a public
information providing step in which the entrustor apparatus provides the
public information to the outsourcer apparatus, a signature key generating
step in which the entrustor apparatus generates a signature key
corresponding to the user apparatus using the public information and the
member registration key, in response to the registration request from the
user apparatus, a signature information providing step in which the entrustor
apparatus provides the signature key and the public information to the user
apparatus, a group signature generating step in which the user apparatus
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generates group signature data using the signature key and the public
information provided by the signature information provider and a request for
the predetermined service, a group signature data providing step in which
the user apparatus provides the group signature data and the request for the
predetermined service to the outsourcer apparatus, an authenticating step in
which the outsourcer apparatus authenticates whether the group signature
data provided by the group signature data provider is legitimate or not using
the public information provided by the public information provider, and a
service providing step in which the outsourcer apparatus provides the
predetermined service to the user apparatus in response to the request for
the predetermined service if the authenticator judges that the group
signature data is legitimate.
An outsourcer apparatus according to the present invention is
connected to a user apparatus and an entrustor apparatus for registering the
user apparatus as a member for receiving a predetermined service when a
registration request for enrolling the user apparatus as the member is
received from the user apparatus, the outsourcer apparatus for providing the
predetermined service to the member which has requested the
predetermined service on behalf of the entrustor apparatus, the arrangement
being such that when the outsourcer apparatus is requested to provide the
predetermined service by the user apparatus, the outsourcer apparatus
authenticates whether the user apparatus is the member or not according to
a group signature scheme, the outsourcer apparatus comprising a receiver
for receiving public information for use in the group signature scheme from
the entrustor apparatus, an authenticaior for authenticating whether group
signature data is legitimate or not using the public information when the
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group signature data and a request for the predetermined service are
received from the user apparatus, and a service provider for providing the
predetermined service to the user apparatus in response to the request for
the predetermined service if the authenticator judges that the group
signature data is legitimate.
A service providing method according to the present invention is to be
carried out by an outsourcer apparatus connected to a user apparatus and
an entrustor apparatus for registering the user apparatus as a member for
receiving a predetermined service when a registration request for enrolling
the user apparatus as the member is received from the user apparatus, the
outsourcer apparatus for providing the predetermined service to the member
which has requested the predetermined service on behalf of the entrustor
apparatus, the arrangement being such that when the outsourcer apparatus
is requested to provide the predetermined service by the user apparatus, the
outsourcer apparatus authenticates whether the user apparatus is the
member or not according to a group signature scheme, the service providing
method comprising a receiving step of receiving public information for use in
the group signature scheme from the entrustor apparatus, an authenticating
step of authenticating whether group signature data is legitimate or not using
the public information when the group signature data and a request for the
predetermined service are received from the user apparatus, and a service
providing step of providing the predetermined service to the user apparatus
in response to the request for the predetermined service if the group
signature data are legitimate.
2 5 According to the pr eseni invention as descriued above, ihe ouisourcer
apparatus authenticates whether the user apparatus is a member of the
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entrustor apparatus or not using only the public information of the entrustor
apparatus according to the group signature scheme. Therefore, the
outsourcer apparatus can determine whether the user apparatus is a
member of the entrustor apparatus or not without using private information of
the member unlike the background art.
Therefore, it is not necessary for the entrustor to provide the private
information that is managed by the entrustor to the outsourcer. It is thus
possible to avoid the danger of the leakage of member information (private
information).
The outsourcer can solely confirm whether the user is a member of the
entrustor or not, without using member information. Therefore, when the
user is to receive a service from the outsourcer, the user does not need to
communicate with the entrustor unlike the background art.
Preferably, the user apparatus generates a group signature key based
on the public information, converting the group signature key into converted
data, and providing the converted data to the entrustor apparatus, the -
entrustor apparatus generates a digital signature using the converted data
provided by the user apparatus and the member registration key, thereby
generating a member certificate as the signature key, and the user
apparatus generates the group signature data using the request for the
predetermined service, the member certificate, the group signature key, and
the public information.
According to the above invention, it is possible to use a group
verification scheme disclosed in Non-patent document 1.
Preferably, the entrustor apparatus acquires the group signature data
from the outsourcer apparatus, and identifies the user apparatus, which has
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provided the group signature data, from among members of the entrustor
apparatus, using the group signature data and the open key.
According to the above invention, the entrustor apparatus can identify
the user apparatus which has requested the predetermined service without
the outsourcer apparatus knowing.
Preferably, the entrustor apparatus calculates a usage fee for the
predetermined service used by the user apparatus and charges the user
apparatus with the calculated usage fee, based on the identified user
apparatus and the request for the predetermined service.
According to the above invention, the entrustor apparatus can charge
the user apparatus which has requested the predetermined service with a
predetermined service usage fee, without the outsourcer apparatus knowing.
Preferably, members of the entrustor apparatus are divided into a
plurality of groups, the entrustor apparatus generates public information, a
member registration key, and an open key for use in the group signature
scheme for each of the groups, provides the public information generated for
each of the groups to the outsourcer apparatus, and responsive to the
registration request and group selecting information from the user apparatus,
selects one of the groups to which the user apparatus belongs based on the
group selecting information, and generates a signature key corresponding to
the user apparatus using the public information and the member registration
key of the selected group, provides the signature key, the public information
of the selected group, and group information indicative of the selected group,
to the user apparatus, the user apparatus provides the group signature data,
the request for the predetermined service, and the group information, to the
outsourcer apparatus, the outsourcer apparatus authenticates whether the
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group signature data is legitimate or not, using the public information of the
group indicated by the group information, and provides the service
corresponding to the group indicated by the group information to the user
apparatus in response to the request for the predetermined service if the
authenticator judges that the group signature data is legitimate.
According to the above invention, it is possible to provide a service
depending on the user apparatus.
Preferably, the service providing system comprises a plurality of the
entrustor apparatus, each of the entrustor apparatus provides the signature
key, the public information, and entrustor apparatus information indicative of
the entrustor apparatus to the user apparatus, the user apparatus provides
the group signature data, the request for the predetermined service, and the
entrustor apparatus information to the outsourcer apparatus, and the
outsourcer apparatus authenticates whether the group signature data is
legitimate or not, using the public information which is provided by the
entrustor apparatus indicated by the entrustor apparatus information.
According to the above invention, the outsourcer apparatus is capable
of receiving service providing services from a plurality of entrustor
apparatus.
A program according to the present invention controls a computer
connected to a user apparatus and an entrustor apparatus for registering the
user apparatus as a member for receiving a predetermined service when a
registration request for enrolling the user apparatus as the member is
received from the user apparatus, the computer for providing the
predetermined service to the member which has requested the
predetermined service on behalf of the entrustor apparatus, the arrangement
being such that when the computer is requested to provide the
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predetermined service by the user apparatus, the computer authenticates
whether the user apparatus is the member or not according to a group
signature scheme, the program enabling the computer to perform a service
process including a receiving process for receiving public information for use
in the group signature scheme from the entrustor apparatus, an
authenticating process for authenticating whether group signature data is
legitimate or not using the public information when the group signature data
and a request for the predetermined service are received from the user
apparatus, and a service proving process for providing the predetermined
service to the user apparatus in response to the request for the
predetermined service if the group signature data are legitimate.
According to the above invention, it is possible for the computer to
perform the above service providing method.
Advantages of the invention:
According to the present invention, since the entrustor is not required to
provide member information that is managed by the entrustor to the
outsourcer, it is possible to avoid the danger of the leakage of private
information. Therefore, when the user is to receive a service from the
outsourcer, the user does not need to communicate with the entrustor.
Brief description of the drawings:
Fig. 1 is a block diagram showing an arrangement according to a first
exemplary embodiment of the present invention;
Fig. 2 is a flowchart of an operation sequence for registering a member
according to the first exemplary embodiment of the present invention;
Fig. 3 is a flowchart of an operation sequence for providing a service
according to the first exemplary embodiment of the present invention;
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Fig. 4 is a block diagram showing an arrangement according to a
second exemplary embodiment of the present invention;
Fig. 5 is a flowchart of an operation sequence for processing a charge
according to the second exemplary embodiment of the present invention;
Fig. 6 is a block diagram showing an arrangement according to a third
exemplary embodiment of the present invention; and
Fig. 7 is a block diagram showing an arrangement according to a fourth
exemplary embodiment of the present invention.
Description of reference characters:
1, la, lb entrustor apparatus
2, 2a outsourcer apparatus
3 user apparatus
4 second entrustor apparatus
5 second user apparatus
101 group key generator
102 public information discloser
103 member registration key memory
104 open key memory
105 member registrar
106 member information memory
107 service log receiver
108 signatory identifier
109 charger
110 charge information memory
1 11 second group key generaior
112 second member registration key memory
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113 second open key memory
201 public information memory
202 service revealer
203 service provider
204 group signature authenticator
205 service log memory
206 service log provider
207 second public information memory
208 second service log memory
209 second service log provider
301 subscriber
302 member certificate memory
303 group signature key memory
304 service selector
305 group signature generator
306 random number generator
307 service requestor
Best mode for carrying out the invention:
A best mode for carrying out the invention will be described in detail
below with reference to the drawings.
A group signature system based on a group signature scheme which is
used in exemplary embodiments shown below will first be described below.
The group signature system comprises a group management
apparatus, a plurality of signature apparatus, and a plurality of
authentication
apparatus. The group managemeni apparatus manages a group, adds
members, and identifies signatories. The signature apparatus generate
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group signature data. The authentication apparatus authenticate group
signature data.
The group signature system operates as follows:
(1) The group management apparatus generates public information, a
member registration key (secret key), and an open key (secret key). The
public information includes at least a public key of the member registration
key (secret key) and a public key of the open key (secret key). The public
information is of a value set commonly for the group. The group
management apparatus secretly holds the member registration key (secret
key) and the open key (secret key).
(2) The group management apparatus generates a signature key from
the public information and the member registration key (secret key), and
issues the signature key to the signature apparatus. The signature
apparatus to which the signature key is issued becomes a member of the
group. The signature key is different from signature apparatus to signature
apparatus. The signature apparatus secretly holds the signature key.
(3) Using the public information and the signature key, the signature
apparatus performs calculations to convert messages and uses the results of
the calculations as the group signature data.
(4) The authentication apparatus receives the messages and the group
signature data, and confirms whether the group signature data are proper or
not using the public information. In other words, the authentication
apparatus confirms whether the group signature data have been properly
calculated by the signature apparatus which has the signature key issued by
the group management apparatus, or not.
(5) If necessary, the group management apparatus identifies the
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signature apparatus which has generated the group signature data, using the
open key (secret key).
The group signature data generated by the signature apparatus include
data certifying that (a) the signature apparatus which have generated the
group signature data is one of legitimate group members whose subscription
has been accepted by the group management apparatus and (b) the group
management apparatus can subsequently identify the signature apparatus,
without leaking any information whatsoever as to the signature apparatus.
The generated group signature data have a value that differs each time they
are generated.
For authenticating the group signature data, the authentication
apparatus confirms whether the group signature data certifies said (a), (b)
properly or not, using the public information. Only the signature apparatus
which has the signature key properly issued from the group signature
apparatus can calculate group signature data that pass the authentication.
According to ordinary digital signature, it is possible to confirm the
legitimacy of a signature using only public information (public key)
corresponding to an individual. Similarly, according to group signature data,
it is also possible to confirm the legitimacy of a signature using only public
information corresponding to a group.
For example, in the group signature system disclosed in Non-patent
document 1, public information includes a parameter common to the system,
and a signature key issued to a signature apparatus comprise a group
signature key and a member certificate.
C The ~ ~~ ~ m
2 ~ ~group s' ~gna~ure key ' ~n ~ of a ~ ~a~u~ rando~ I f~ywselected by the
signature apparatus and the group management apparatus which cooperate
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with each other, based on the public information (common parameter). This
value is only known to the signature apparatus. The group signature key
represents data required to prevent the group management apparatus from
falsifying the signature.
The member certificate is a digital signature generated by calculations
for converting converted data of the group signature key using a member
registration key (secret key).
For generating group signature data for a message, the signature
apparatus encrypts the member certificate with a public key corresponding to
an open key. The encrypted member certificate is referred to as encrypted
data. The signature apparatus then calculates converted data of the
member certificate.
Then, the signature apparatus calculates certification data for certifying
two conditions, i.e., (a) the value (namely, the member certificate) kept
secret
by the encrypted data and the converted data satisfies a formula for
authenticating the digital signature for the converted data of the group
signature key, and (b) the encrypted data are data generated by encrypting
the value satisfying the condition (a) with the public key corresponding to
the
open key, using the message, the public information, the member certificate,
the group signature key, the encrypted data, and the converted data.
Then, the signature apparatus outputs the encrypted data, the
converted data, and the certification data as group signature data.
An authentication apparatus confirms whether the certification data
included in the group signature data properly certifies the conditions (a) and
(b) or not, using the message, the group signature data, and the public
information.
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Only the signature apparatus which is aware of the member certificate
and the group signature key that are properly issued by the group
management apparatus is capable of calculating certification data which can
pass the authentication.
The group management apparatus decrypts the encrypted data
included in the group signature data using the open key (secret key). Then,
the group management apparatus seeks one, which agrees with the
decrypted data, of the member certificates of all the signature apparatus that
have been left upon issuance of the signature key. The signature apparatus
corresponding to the member certificate that agrees with the decrypted data
is the signature apparatus which has generated the group signature data.
[1st exemplary embodiment]
Fig. 1 is a block diagram showing a service providing system according
to a first exemplary embodiment of the present invention.
As shown in Fig. 1, the service providing system, which employs a
group signature scheme, comprises entrustor apparatus 1, outsourcer
apparatus 2, and at least one user apparatus 3.
Entrustor apparatus 1 includes functions which the group management
apparatus of a group signature system has. Outsourcer apparatus 2
includes functions which the authentication apparatus of the group signature
system has. User apparatus 3 includes functions which the signature
apparatus of the group signature system has.
Entrustor apparatus 1 comprises group key generator 101, public
information discloser 102, member registration key memory 103, open key
memory 104, member registrar 106, member information memory 106,
service log receiver 107, and signatory identifier 108.
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If entrustor apparatus 1 includes a memory storing therein a program
for controlling operation of entrustor apparatus 1 and a computer for
executing the program, then the computer may execute the program to
realize group key generator 101, public information discloser 102, member
registrar 105, service log receiver 107, and signatory identifier 108, and the
memory may realize member registration key memory 103, open key
memory 104, and member information memory 106.
Outsourcer apparatus 2 comprises public information memory 201,
service revealer 202, service provider 203, group signature authenticator
204, service log memory 205, and service log provider 206.
If outsourcer apparatus 2 includes a memory storing therein a program
for controlling operation of outsourcer apparatus 2 and a computer for
executing the program, then the computer may execute the program to
realize service revealer 202, service provider 203, group signature
authenticator 204, and service log provider 206, and the memory may realize
public information memory 201 and service log memory 205.
User apparatus 3 comprises subscriber 301, member certificate
memory 302, group signature key memory 303, service selector 304, group
signature generator 305, random number generator 306, and service
requestor 307.
If user apparatus 3 includes a memory storing therein a program for
controlling operation of user apparatus 3 and a computer for executing the
program, then the computer may execute the program to realize subscriber
301, service selector 304, group signature generator 305, random number
generator 306, and service requestor 307, and the memory may reaiize
member certificate memory 302 and group signature key memory 303.
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Entrustor apparatus 1 is used by the entrustor.
Group key generator 101 generates public information, a member
registration key (secret key), and an open key (secret key) used in the group
signature scheme. The public information includes at least a public key
corresponding to the member registration key (secret key), a public key
corresponding to the open key (secret key), and common parameters used
in the group signature scheme.
Group key generator 101 provides the public information to public
information discloser 102. Group key generator 101 provides the member
registration key to member registration key memory 103. Group key
generator 101 provides the open key to open key memory 104.
Public information discloser 102 stores the public information
generated by group key generator 101.
Member registration key memory 103 stores the member registration
key (secret key) generated by group key generator 101.
Open key memory 104 stores the open key (secret key) generated by
group key generator 101.
When member registrar 105 receives a subscription request (a
registration request to become a member for receiving a certain service) and
information (private information of the user of user apparatus 3, i.e., member
information) about user apparatus 3 from subscriber 301 of user apparatus
3, member registrar 105 registers user apparatus 3 as a member.
Furthermore, member registrar 105 generates a member certificate for
generating group signature data, based on the group signature scheme.
2 5 Member r egistr ar i 05 issues ti 1e member lel Lif il;cte and the public
information to user apparatus 3.
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Member registrar 105 stores the private information and the member
certificate, as related to each other, in member information memory 106.
Member information memory 106 stores the private information and the
member certificate, as related to each other, for each user apparatus.
When service log receiver 107 receives a service log from service log
provider 206 of outsourcer apparatus 2, service log receiver 107 provides the
service log to signatory identifier 108. The service log includes group
signature data generated by user apparatus 3.
When signatory identifier 108 receives the service log from service log
receiver 107, signatory identifier 108 identifies the user apparatus, which
has
generated the group signature data included in the service log, based on the
group signature scheme, using the service log, the public information stored
in public information discloser 102, the open key (secret key) stored in open
key memory 104, and the member certificates of all the members stored in
member information memory 106.
Outsourcer apparatus 2 is used by the outsourcer.
Public information memory 201 stores the public information provided
by public information discloser 102 of entrustor apparatus 1.
Service revealer 202 reveals a list of services provided by outsourcer
apparatus 2 to user apparatus 3. The list represents services entrusted by
entrustor. Service revealer 202 also sends information (service information)
corresponding to the services and additional information thereof to service
selector 304 of user apparatus 3.
Service provider 203 receives service request data from service
requesior 307 of user apparatus 3. The service request data include group
signature data generated by user apparatus 3.
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When service provider 203 receives the service request data frorp
service requestor 307, service provider 203 asks group signature
authenticator 204 to authenticate the group signature data included in the
service request data.
If group signature authenticator 204 judges that the group signature
data are legitimate, then service provider 203 provide the services to user
apparatus 3.
Service provider 203 also provides the service request data to service
log memory 205.
Group signature authenticator 204 authenticates the group signature
data provided by service provider 203 based on the group signature scheme,
using the public information stored in public information memory 201.
Service log memory 205 stores the service request data provided by
service provider 203 as the service log.
Service log provider 206 sends the service log stored in service log
memory 205 to entrustor apparatus 1.
User apparatus 3 is used by the user.
Subscriber 301 communicates with member registrar 105 of entrustor
apparatus 1 to notify entrustor apparatus 1 of a subscription request and
private information of the user of user apparatus 3.
When a member registration and subscription is permitted, subscriber
301 generates a group signature key, and thereafter receives a member
certificate and public information from member registrar 105.
Subscriber 301 provides the member certificate to member certificate
i i iemoi y 302, and provides ii ie group signature key to group signature key
memory 303. For example, subscriber 301 provides the public information
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together with the member certificate to member certificate memory 302.
When group signature data are calculated, subscriber 301 may acquire
public information from public information discloser 102 of entrustor
apparatus 1,and provide the public information to group signature generator
305.
Member certificate memory 302 stores the member certificate and the
public information provided by subscriber 301.
Group signature key memory 303 stores the group signature key
provided by subscriber 301.
Service selector 304 selects a service specified by the user, from the
services revealed by service revealer 202 of outsourcer apparatus 2.
When service selector 304 receives service information and additional
information from service revealer 202, service selector 304 sends the service
information and the additional information to group signature generator 305.
Group signature generator 305 calculates group signature data based
on the group signature scheme, using the service information and the
additional information received from service selector 304, the public
information stored in public information discloser 102 of entrustor apparatus
1, the member certificate stored in member certificate memory 302, the
group signature key stored in group signature key memory 303, and a
random number generated by random number generator 306.
Group signal generator 305 provides the service information and the
additional information received from service selector 304 and the group
signature data to service requestor 307.
Random number generator .3~v6 provides the random number to group
signal generator 305.
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When service requestor 307 receives the service information, the
additional information, and the group signature data from group signal
generator 305, service requestor 307 sends the service information, the
additional information, and the group signature data as service request data
to outsourcer apparatus 2.
Operation of the first exemplary embodiment will be described below.
(Key generation)
First, in entrustor apparatus 1, group key generator 101 generates
public information, a member registration key, and an open key used in the
group signature system. Group key generator 101 provides the public
information to public information discloser 102, provides the member
registration key (secret key) to member registration key memory 103, and
provides the open key (secret key) to open key memory 104.
(Key notification)
The entrustor makes a contract with the outsourcer for entrusting
outsourcer apparatus 2 to provide services for members of the entrustor.
Public information discloser 102 of entrustor apparatus 1 sends the
public information stored in public information discloser 102 as information
required for member authentication to outsourcer apparatus 2.
When public information memory 201 of outsourcer apparatus 2
receives the public information, public information memory 201 stores the
public information.
(Member registration)
Based on an operation made by the user, user apparatus 3 causes
entri.istor apparatus 1 to per for i i i a user registration process and
acquires
information required to generate group signature data from entrustor
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apparatus 1. This process need once in user registration.
It is assumed that entrustor apparatus 1 has revealed information
required to become a member of entrustor apparatus 1.
Fig. 2 is a flowchart of an operation sequence for registering a member.
Those parts shown in Fig. 2 which are identical to those shown in Fig. 1 are
denoted by identical reference characters.
An operation sequence for registering a member will be described
below with reference to Fig. 2.
When subscriber 301 of user apparatus 3 has received private
information (e.g., name, address, and age) required become a member of
entrustor apparatus 1 from the user, subscriber 301 executes step S101.
In step S101, subscriber 301 sends the private information and a
subscription request to entrustor apparatus 1. When subscriber 301 has
sent the private information and the subscription request to entrustor
apparatus 1, member registrar 105 of entrustor apparatus 1 executes step
S102.
In step S102, member registrar 105 receives the private information
and the subscription request. When member registrar 105 has received the
private information and the subscription request, member registrar 105
executes step S 103.
In step S103, member registrar 105 determines whether the user with
the private information is allowed to become a member of the entrustor or
not, based on the private information. For example, member registrar 105
determines whether the age indicated by the private information satisfies a
member subscription i r equir ei i iei it or not.
If member registrar 105 makes a judgment to refuse to register the
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user as a member of the entrustor (subscription), then member registrar 105
notifies user apparatus 3 of a subscription refusal. When user apparatus 3
has received the subscription refusal, user apparatus 3 executes step S104.
In step S104, subscriber 301 of user apparatus 3 displays a message
representing the subscription refusal, for example, and stops the subscription
process.
If member registrar 105 makes a judgment to permit a subscription,
then member registrar 105 executes step S105, and subscriber 301
executes step S 106.
In steps S105, S106, member registrar 105 communicates with
subscriber 301 to generate a signature key required to generate group
signature data, using the public information stored in public information
discloser 102 and the member registration key stored in member registration
key memory 103. The signature key is made up of a member certificate and
a group signature key. The group signature key is generated by subscriber
301 and represents information that is known only to user apparatus 3.
As a result of the above process, member registrar 105 acquires the
member certificate and subscriber 301 acquires the member certificate and
the group signature key.
Member registrar 105 stores the initially received private information in
relation to the member certificate in member information memory 106.
Subscriber 301 stores the member certificate in member certificate
memory 302 and stores the group signature key in group signature key
memory 303.
(Service usage)
In service usage, user apparatus 3 receives services for the members
CA 02609973 2007-11-28
from outsourcer apparatus 2.
Fig. 3 is a flowchart of an operation sequence for using a service.
Those parts shown in Fig. 3 which are identical to those shown in Fig. 1 are
denoted by identical reference characters.
An operation sequence for using a service will be described below with
reference to Fig. 3.
In step S201, service selector 304 of user apparatus 3 receives a
revealed service list from service revealer 202 of outsourcer apparatus 2.
User apparatus 3 displays the service list.
When the user has operated user apparatus 3 to specify a service,
which the user wants to receive, from the service list, service selector 304
executes step S202.
In step S202, service selector 304 selects the specified service from
the service list, and sends a selection result representing the selected
service to service revealer 202.
When service revealer 202 has received the selection result, service
revealer 202 executes step S203.
In step S203, service revealer 202 sends information (service
information) corresponding to the selected service and additional information
to service selector 304.
The additional information represents information required to make
unique a message to be signed. For example, the additional information is a
session ID, time information, or a random number generated by outsourcer
apparatus 2.
vvllen ser\/ice revec.ller 202 has sent the information (service
information) and the additional information to service selector 304, service
26
CA 02609973 2007-11-28
selector 304 executes step S204.
In step S204, service selector 304 receives the service information and
the additional information from service revealer 202, and sends the service
information and the additional information to group signature generator 305.
When group signature generator 305 has received the service
information and the additional information from service selector 304, group
signature generator 305 executes step S205.
In step S205, group signature generator 305 calculates group signature
data corresponding to the service information and the additional information,
based on the group signature scheme, using the public information stored in
public information discloser 102 of entrustor apparatus 1, the member
certificate stored in member certificate memory 302, the group signature key
stored in group signature key memory 303, and the random number
generated by random number generator 306.
The group signature data are data indicating that user apparatus 3 is a
member of entrustor apparatus 1.
Group signature generator 305 provides the service information, the
additional information, and the group signature data to service requestor
307.
When service requestor 307 has received the service information, the
additional information, and the group signature data from group signature
generator 305, service requestor 307 executes step S206.
In step S206, service requestor 307 sends service request data
including the service information, the additional information, and the group
signature data to service provider 203 of outsourcer apparatus 2.
When service provider 203 has received the service request data from
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service requestor 307, service provider 203 executes step S207.
In step S207, service provider 203 notifies group signature
authenticator 204 of the service request data in order to authenticate the
legitimacy of the group signature data included in the service request data.
When group signature authenticator 204 has received the service
request data from service provider 203, group signature authenticator 204
executes step S208.
In step S208, group signature authenticator 204 authenticates the
group signature data included in the service request data based on the group
signature scheme, using the public information stored in public information
memory 201.
Group signature authenticator 204 notifies service provider 203 of the
authentication result.
When service provider 203 has received the authentication result from
group signature authenticator 204, service provider 203 executes step S209.
In step S209, service provider 203 confirms whether the authentication
result indicates that the group signature data are legitimate or not.
If the authentication result indicates that the group signature data are
legitimate, then service provider 203 executes step S210. If the
authentication result indicates that the group signature data are not
legitimate, then service provider 203 executes step S212.
- In step S210, service provider 203 judges that user apparatus 3 is a
member of entrustor apparatus 1, and provides the service requested by
user apparatus 3 to user apparatus 3.
After having prov,d,ng the serv,ce, service pr ov,der 203 executes step
S211.
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In step S21 1, service provider 203 saves the service information, the
additional information, and the group signature data as the service log in
service log memory 205.
In step S212, service provider 203 stops the service using operation.
(User identification)
Entrustor apparatus 1 identifies user apparatus 3, which has received
the service, based on the service log saved in outsourcer apparatus 2. This
process is performed to identify user apparatus 3 which has received the
service in the event that a problem has occurred between outsourcer
apparatus 2 and user apparatus 3 while the service is being provided.
Service log provider 206 selects a set of service information, additional
information, and group signature data corresponding to a session (service
log) in which user apparatus 3 will be identified, from the service log saved
in
service log memory 205.
Service log provider 206 sends the service information, the additional
information, and the group signature data to service log receiver 107 of
entrustor apparatus 1.
When service log receiver 107 receives the service information, the
additional information, and the group signature data from service log provider
206, service log receiver 107 sends the service information, the additional
information, and the group signature data to signatory identifier 108.
Signatory identifier 108 identifies the user apparatus, which has
generated the group signature data, based on the group signature scheme,
using the public information stored in public information discloser 102, the
open key stored in open key memory 104, the member certificates of all the
members stored in member information memory 106, and the service
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CA 02609973 2007-11-28
information, the additional information, and the group signature data sent
from service log receiver 107.
There may be a case in which the user does not want entrustor
apparatus 1 to know the service that the user has received via user
apparatus 3. In such a case, group signature generator 305 of user
apparatus 3 calculates group signature data while not including the service
information in the data to be signed.
Advantages of the exemplary embodiment will be described below.
According to the exemplary embodiment, outsourcer apparatus 2
authenticates a member of entrustor apparatus I using only the public
information of entrustor apparatus 1.
Therefore, outsourcer apparatus 2 does not require the member
information managed by entrustor apparatus 1. It is not necessary for the
entrustor to provide the private information that is managed by the entrustor
to the outsourcer. It is thus possible to avoid the danger of the leakage of
the private information that is managed by the entrustor from outside entities
such as the outsourcer.
For the same reasons, the outsourcer can reduce the cost for
managing the private information. Furthermore, the possibility that the
private information of the user may be obtained by a third party other than
the entrustor is reduced.
In the event that a problem has occurred while the service is being
provided, the outsourcer can ask the entrustor to identify the user apparatus
which has received the service.
User apparatus 3 can cause outsourcer apparatus 2 to confirm thai
user apparatus 3 is a member of entrustor apparatus 1 by presenting the
CA 02609973 2007-11-28
group signature data generated by user apparatus 3. User apparatus 3 is
thus not required to communicate with entrustor apparatus 1 when using the
service.
According to the exemplary embodiment, user apparatus 3 generates a
group signature key based on public information, converts the group
signature key to generate converted data, and provides the converted data to
entrustor apparatus 1. Entrustor apparatus 1 encrypts the converted data
with a member registration key to generate a member certificate as a
signature key, and provides the member certificate to user apparatus 3.
User apparatus 3 generates group signature data using the request for the
desired service, the member certificate, the group signature key, and the
public information.
Consequently, the group authentication scheme disclosed in Non-
patent document 1 can be used as the group authentication scheme.
In the exemplary embodiment, entrustor apparatus 1 acquires the
group signature data from outsourcer apparatus 2, and identifies user
apparatus 3, which has provided the group signature data, among the
members, using the group signature data and the open key.
Entrustor apparatus 1 is thus capable of identifying user apparatus 3,
which has requested the desired service, without outsourcer apparatus 2
knowing.
[2nd exemplary embodiment]
A service providing system according to a second exemplary
embodiment of the present invention will be described below with reference
to the drawings.
Fig. 4 is a block diagram showing the present service providing system.
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Those parts shown in Fig. 4 which are identical to those shown in Fig. 1 are
denoted by identical reference characters.
As shown in Fig. 4, the present service providing system includes
entrustor apparatus 1 a, outsourcer apparatus 2, and user apparatus 3.
Entrustor apparatus 1 a comprises the arrangement of entrustor
apparatus 1, charger 109, and charging information memory 110.
If entrustor apparatus 1 a includes a memory storing therein a program
for controlling operation of entrustor apparatus 1 a and a computer for
executing the program, then the computer may execute the program to
realize charger 109, and the memory may realize charging information
memory 110.
Charger 109 totals service usage statuses of user apparatus based on
users identified by signatory identifier 108. Charger 109 determines usage
fees of the respective users based on the information stored in charging
information memory 110, and notifies (charges) the user apparatus of (with)
the usage fees.
Charging information memory 110 stores information about a charging
method for service usage. The charging method may be, for example, a
pay-as-you-go method depending on the number of times that a service is
used, or a charging method depending on the type of a service used.
Outsourcer apparatus 2 and user apparatus 3 are identical in
arrangement to outsourcer apparatus 2 and user apparatus 3 according to
the first exemplary embodiment.
Operation of the second exemplary embodiment will be described
below.
The key generation of entrustor apparatus 1 a, the notification of
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CA 02609973 2007-11-28
outsourcer apparatus 2 of the public information, the process of registering
user apparatus 3 to subscribe to entrustor apparatus 1 a, and the process of
making the user apparatus use the service are carried out in the same
manner as with the first exemplary embodiment.
(Charging process)
Fig. 5 is a flowchart of an operation sequence for processing a charge.
Those parts shown in Fig. 5 which are identical to those shown in Fig. 1 are
denoted by identical reference characters. The operation sequence for
processing a charge will be described below with reference to Fig. 5.
Entrustor apparatus 1 a collects the service log from outsourcer
apparatus 2 per constant interval.
Specifically, service log provider 206 of outsourcer apparatus 2
executes step S301 per constant time.
In step S301, service log provider 206 reads the service log from
service log memory 205. When service log provider 206 has read the
service log, service log provider 206 executes step S302.
In step S302, service log provider 206 sends the service log to service
log receiver 107 of entrustor apparatus 1. The service log may be sent and
received off-line, rather than via a network.
When service log provider 206 has sent the service log, service log
receiver 107 executes step S303.
In step S303, service log receiver 107 receives the service log from
service log provider 206, and sends service information, additional
information, and group signature data included in the service log to signatory
identifier 108.
When signatory identifier 108 has received the service information, the
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CA 02609973 2007-11-28
additional information, and the group signature data, signatory identifier 108
executes step S304.
In step S304, signatory identifier 108 identifies the user apparatus,
which have generated the group signature data, based on the group
signature scheme, using the group signature data, the pubiic information
stored in public information discloser 102, the open key stored in open key
memory 104, and the member certificates of all the members stored in
member information memory 106.
When signatory identifier 108 identifies all the user apparatus in the
service log, signatory identifier 108 provides the service information and
user
apparatus information representing the identified user apparatus to charger
109.
When charger 109 has received the service information and the user
apparatus information, charger 109 executes step S305.
In step S305, charger 109 totals service usage statuses of the user
apparatus based on the service information and the user apparatus
information. When charger 109 has totaled service usage statuses, charger
109 executes step S306.
In step S306, charger 109 calculates usage fees of the respective user
apparatus according to the usage statuses and the charging method stored
in charging information memory 110. When charger 109 has calculated
usage fees of the respective user apparatus, charger 109 executes step
S307.
In step S307, charger 109 notifies (charges) the user apparatus of
(with) the calculated usage results.
Advantages of the present exemplary embodiment will be described
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CA 02609973 2007-11-28
below.
According to the exemplary embodiment, entrustor apparatus 1 a
receives a service log from outsourcer apparatus 2, and identifies a user
apparatus which has generated group signature data included in the service
log, using a signature identifying function of the group signature system.
Therefore, the entrustor apparatus is capable of identifying the user
apparatus, which has requested the desired service, without the outsourcer
apparatus knowing.
Based on the identified user apparatus and the request for the desired
service, entrustor apparatus 1 a calculates the fee for the usage of the
desired service by the user apparatus, and charges the user apparatus with
the usage fee.
Consequently, entrustor apparatus 1 a is capable of charging the user
apparatus which has requested the desired service with the service usage
fee without the outsourcer apparatus knowing.
[3rd exemplary embodiment]
A service providing system according to a third exemplary embodiment
of the present invention will be described below with reference to the
drawings.
Fig. 6 is a block diagram showing the present service providing system.
Those parts shown in Fig. 6 which are identical to those shown in Fig. 1 are
denoted by identical reference characters.
According to the third exemplary embodiment, entrustor apparatus lb
sets a plurality of groups as members. In a member registering process,
entrustor apparatus lb determines a group to which user apparatus 3 wi!l
belong, depending on the qualification of user apparatus 3, and issues a
CA 02609973 2007-11-28
group signature key corresponding to the group.
A group setting method may be, for example, a method of classifying
groups based on member qualifications, e.g., member fees, or a method of
classifying groups based on private information, e.g., male and female.
Outsourcer apparatus 2a changes services to be provided to user
apparatus 3 depending on the group to which user apparatus 3 belongs.
As shown in Fig. 6, the service providing system comprises entrustor
apparatus 1 b, outsourcer apparatus 2a, and user apparatus 3.
Entrustor apparatus 1 b includes a plurality of group key generators, a
plurality of member registration key memories, and a plurality of open key
memories.
Fig. 6 shows an example in which entrustor apparatus 1 b includes two
group key generators, two member registration key memories, and two open
key memories. Specifically, entrustor apparatus 1 b comprises the
arrangement of entrustor apparatus 1 shown in Fig. 1 or the arrangement of
entrustor apparatus 1 a shown in Fig. 4, second group key generator 111,
second member registration key memory 112, and second open key memory
113.
If entrustor apparatus 1 b includes a memory storing therein a program
for controlling operation of entrustor apparatus 1 b and a computer for
executing the program, then the computer may execute the program to
realize second group key generator 111, and the memory may realize
second member registration key memory 112 and second open key memory
113.
As with i group key generator 101, second group key generator 111
generates second public information, a second member registration key
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CA 02609973 2007-11-28
(secret key), and a second open key (secret key) used in the group signature
system.
Second group key generator 111 provides the second public
information to public information discloser 102, provides the second member
registration key to second member registration key memory 112, and
provides the second open key to second open key memory 113.
Second member registration key memory 112 stores the second
member registration key generated by second group key generator 111.
Second open key memory 113 stores the second open key generated
by second group key generator 111.
Outsourcer apparatus 2a comprises the arrangement of outsourcer
apparatus 2 and second public information memory 207.
Second public information memory 207 stores the second public
information sent from public information discloser 102 of entrustor apparatus
1b.
User apparatus 3 is identical in arrangement to user apparatus 3
according to the first exemplary embodiment.
Operation of the third exemplary embodiment will be described below.
(Key generation)
First, in entrustor apparatus 1 b, group key generator 101 and second
group key generator 111 generate respective keys used in the group
signature system.
Group key generator 101 provides the first public information to public
information discloser 102, provides the first member registration key to
member registration key memory 103, and provides the first open key to
open key memory 104.
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Second group key generator 111 provides the second public
information to public information discloser 102, provides the second member
registration key to second member registration key memory 112, and
provides the second open key to second open key memory 113.
(Key notification)
Public information discloser 102 of entrustor apparatus lb sends the
first public information and the second public information to outsourcer
apparatus 2a.
In outsourcer apparatus 2a, public information memory 201 stores the
second public information, and second public information memory 207 stores
the second public information.
The group corresponding to the first public information will hereinafter
referred to as group 1, and the group corresponding to the second public
information as group 2.
(Member registration)
Based on an operation made by the user, user apparatus 3 causes
entrustor apparatus 1 b to perform a user registration process and acquires
information required to generate group signature data from entrustor
apparatus lb. This process is required only once upon member registration.
An operation sequence for registering a member will be described
below again with reference to Fig. 2.
The user enters private information (e.g., name and address) required
to become a member of entrustor apparatus 1 b, and information (group
selecting information) required to select a group to which the user is to
belong, inio user apparatus 3.
For example, if a group to which the user is to belong is classified by
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CA 02609973 2007-11-28
member qualification, then the user enters a desired member qualification as
group selecting information into user apparatus 3. If a group to which the
user is to belong is classified by gender of the user, then the user enters
gender information as group selecting information into user apparatus 3.
In the present exemplary embodiment, it is assumed that the user
enters a member qualification as group selecting information into user
apparatus 3.
When subscriber 301 of user apparatus 3 has received the private
information and the group selecting information from the user, subscriber
301 executes step S 101.
In step S101, subscriber 301 sends the private information, the group
selecting information, and a subscription request to entrustor apparatus 1 b.
When subscriber 301 has sent the private information, the group
selecting information, and the subscription request to entrustor apparatus 1
b,
member registrar 105 executes step S102.
In step S102, member registrar 105 receives the private information,
the group selecting information, and the subscription request. When
member registrar 105 has received the private information, the group
selecting information, and the subscription request, member registrar 105
executes step S103.
In step S103, member registrar 105 determines whether the user with
the private information is allowed to become a member of the entrustor or
not, based on the private information.
If member registrar 105 makes a judgment to permit a subscription,
then member registrar 105 selects a group to which the user is to belong,
according to the group selecting information.
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In the present exemplary embodiment, member registrar 105 selects
either group 1 or group 2.
When member registrar 105 has selected a group, member registrar
105 executes step S105.
In step S105, member registrar 105 communicates with subscriber 301
to generate a signature key required to generate group signature data of the
selected group, using the public information of the selected group and the
member registration key. Member registrar 105 provides the signature key
and group information representative of the selected group to user apparatus
3.
Subsequent operation is the same as the operation of the first
exemplary embodiment.
(Service usage)
In service usage, user apparatus 3 receives services for the members
from outsourcer apparatus 2a.
Outsourcer apparatus 2a changes services to be provided to user
apparatus 3 depending on the group to which user apparatus 3 belongs.
An operation sequence in which only user apparatus 3 belonging to
group 2 receives a service will be described below.
The operation sequence which is different from the operation of the
first exemplary embodiment will mainly be described below again with
reference to Fig. 3.
In step S206 shown in Fig. 3, service requestor 307 sends the service
information, the additional information, the group signature data, and the
2 5 information (group information) representing ihe group to which user
apparatus 3 belongs, to service provider 203 of outsourcer apparatus 2.
CA 02609973 2007-11-28
In the present exemplary embodiment, the group information
representative of "group 2" is sent.
In step S207, service provider 203 notifies group signature
authenticator 204 of the service request data and the group information
(group 2) in order to authenticate the legitimacy of the group signature data
included in the service request data.
When group signature authenticator 204 has received the service
request data and the group information from service provider 203, group
signature authenticator 204 executes step S208.
In step S208, group signature authenticator 204 selects public
information to be used according to the group information (group 2).
In the present exemplary embodiment, group signature authenticator
204 authenticates the group signature data using the second public
information stored in second public information memory 207, and notifies
service provider 203 of the authentication result.
In step S209, if the authentication result indicates that the group
signature data are legitimate, then service provider 203 judges that user
apparatus 3 belongs to group 2 and executes step S210. After having
providing the service, service provider 203 executes step S21 1.
In step S21 1, service provider 203 saves the service information, the
additional information, the group signature data, and the group information in
service log memory 205.
(User identification)
When signatory identifier 108 has received the service log, signatory
identifier 108 selects the open key stored in open key memory 104 or the
second open key stored in second open key memory 113 according to the
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group information included in the service log. Signatory identifier 108
identifies the user apparatus which has generated the group signature data
included in the service log, using the selected open key.
Advantages of the present exemplary embodiment will be described
below.
According to the present exemplary embodiment, entrustor apparatus
1 b sets a plurality of groups to which user apparatus 3 is able to belong,
and
outsourcer apparatus 2a authenticates whether the user apparatus is a
member of entrustor apparatus 1 b in each of the groups or not according to
the group signature scheme.
Therefore, it is possible to provide a service matching the user
apparatus.
Outsourcer apparatus 2a can confirm the qualification or part of the
private information of user apparatus 3, and hence can set a finer service
providing range.
[4th exemplary embodiment]
A service providing system according to a fourth exemplary
embodiment of the present invention will be described below with reference
to the drawings.
Fig. 7 is a block diagram showing the present service providing system.
Those parts shown in Fig. 7 which are identical to those shown in Fig. 6 are
denoted by identical reference characters.
According to the fourth exemplary embodiment, outsourcer apparatus
2b is entrusted with the supply of services by a plurality of entrustor
apparatus. Fig. 7 shows in block form an example in which outsourcer
apparatus 2b provides an identical service to members of two entrustor
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apparatus.
As shown in Fig. 7, the present service providing system comprises
entrustor apparatus 1, outsourcer apparatus 2b, user apparatus 3, second
entrustor apparatus 4, and second user apparatus 5.
Entrustor apparatus 1 and second entrustor apparatus 4 are identical in
arrangement to entrustor apparatus 1 shown in Fig. 1 or entrustor apparatus
1 a shown in Fig. 4.
Outsourcer apparatus 2b includes second service log memory 208 and
second service log provider 209 in addition to the arrangement of outsourcer
apparatus 2a.
If outsourcer apparatus 2b includes a memory storing therein a
program for controlling operation of outsourcer apparatus 2b and a computer
for executing the program, then the computer may execute the program to
realize second service log provider 209, and the memory may realize second
service log memory 208.
Second service log memory 208 stores service request data provided
by a member of second entrustor apparatus 4 as a service log.
Second service log provider 209 sends the service log stored in second
service log memory 208 to second entrustor apparatus 4.
User apparatus 3 and second user apparatus 5 are identical in
arrangement to user apparatus 3 shown in Fig. 1.
Operation of the fourth exemplary embodiment will be described below.
Keys are generated by entrustor apparatus 1 and second entrustor
apparatus 4 in the same manner as a key is generated according to the first
exemplary embodiment. Entrustor apparatus 1 sends public information
thereof to outsourcer apparatus 2b. Second entrustor apparatus 4 sends
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public information thereof to outsourcer apparatus 2b.
In outsourcer apparatus 2b, public information memory 201 stores the
public information of entrustor apparatus 1, and second public information
memory 207 stores the public information of second entrustor apparatus 4.
User apparatus 3 registers itself as a member in entrustor apparatus 1
and acquires a signature key. At this time, entrustor apparatus 1 provides
entrustor apparatus information indicative of entrustor apparatus 1, together
with the signature key, to user apparatus 3.
Second user apparatus 5 registers itself as a member in second
entrustor apparatus 4 and acquires a signature key. At this time, second
entrustor apparatus 4 provides entrustor apparatus information indicative of
entrustor apparatus 4, together with the signature key, to user apparatus 5.
When user apparatus 3 or second user apparatus 5 is to receive a
service from outsourcer apparatus 2b, the user apparatus sends data
(entrustor apparatus information) indicative of the entrustor apparatus to
which the user apparatus belongs, in addition to the service information, the
additional information, and the group signature data, in step S206 shown in
Fig. 3.
In step S208, group signature authenticator 204 judges the entrustor
apparatus to which user apparatus 3 belongs based on the data (entrustor
apparatus information) indicative of the entrustor apparatus, and thereafter
authenticates the group signature data, using the public information
corresponding to the judged entrustor apparatus.
In step S21 1, service provider 203 stores the service log in service log
memory 205 or second service log memory 208 according to the daia
(entrustor apparatus information) indicative of the entrustor apparatus to
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which user apparatus 3 belongs.
In outsourcer apparatus 2b, service log provider 206 sends the service
log for the member of entrustor apparatus 1 to entrustor apparatus 1.
Second service log provider 209 sends the service log for the members of
second entrustor apparatus 4 to second entrustor apparatus 4.
In the present exemplary apparatus, entrustor apparatus 1 and second
entrustor apparatus 4 entrust outsourcer apparatus 2b with the supply of the
same service. However, they may entrust outsourcer apparatus 2b with the
supply of different services.
Advantages of the present exemplary embodiment will be described
below.
According to the present exemplary embodiment, outsourcer apparatus
2 authenticates a user apparatus according to the group signature scheme
for each of the entrustor apparatus.
Therefore, outsourcer apparatus 2 can be entrusted with services from
a plurality of entrustor apparatus.
Embodiments
[Embodiment 1]
A first embodiment of the present invention will be described below with
reference to Fig. 1. The present embodiment corresponds to the first
exemplary embodiment of the present invention.
A group signature system used in the present embodiment is based on
the group signature scheme disclosed in Non-patent document 1.
(Key generation)
fnitiaily, group key generator 101 of entrustor apparatus 1 defines
constants common to the service providing system.
CA 02609973 2007-11-28
First, group key generator 101 defines security parameters F, k, Ip.
Then, group key generator 101 selects ;. 1, 2. 2, y 1, y 2 such that
theysatisfy ~.1 > ~ (~, 2 + k ) , ;~ 2>41p, y 1 > E (y2+k), y 2 > ;L 1 +2.
Then, group key generator 101 defines collision-resistant hash function
H.
Then, group key generator 101 provides E , k, lp, ;~ 1, ;L 2, y 1, y 2, H
to public information discloser 102.
Next, group key generator 101 generates a member registration key.
First, group key generator 101 selects prime numbers p', q' having a
magnitude of Ip bits.
Then, group key generator 101 calculates p= 2p' + 1, q= 2q' + 1, and
establishes n = pq.
Then, group key generator 101 randomly selects a, aO, g, h from a
group of quadratic residues of n.
Then, group key generator 101 provides (p', q') to member registration
key memory 103, and provides (n, a, aO, g, h) to public information discloser
102.
Then, group key generator 101 generates an open key.
Group key generator 101 randomly selects x from a multiplicative group
of prime numbers p'q', and calculates y = g~x mod n.
Group key generator 101 provides x to open key memory 104, and
provides y to public information discloser 102.
(Key notification)
Entrustor apparatus 1 sends parameters k, Ip, ;, 1, ~ 2, y 1, y 2),
collision-resistant hash function H, and public keys (n, a, aO, g, h, y) which
have been disclosed to public information discloser 102, to outsourcer
46
CA 02609973 2007-11-28
apparatus 2 which has been contracted.
Outsourcer apparatus 2 stores these values in public information
memory 201.
(Member registration)
User apparatus 3 requests entrustor apparatus 1 to register itself as a
member. First, user apparatus 3 sends private information required for a
member registration and a subscription request to entrustor apparatus 1.
The private information represents "name", "address", and "mail address",
for example.
When entrustor apparatus 1 has received the private information and
the subscription request, entrustor apparatus 1 determines whether a
subscription for user apparatus 3 is permitted or not.
If entrustor apparatus 1 permits a subscription for user apparatus 3,
then entrustor apparatus 1 sends information representing a permission to
user apparatus 3.
When a subscription for user apparatus 3 has been permitted,
entrustor apparatus 1 and user apparatus 3 cooperate with each other in
generating a signature key for generating group signature data.
As a result of the generating process, user apparatus 3 acquires group
signature key xi and a member certificate (Ai, ei) which satisfies:
[Equation 1]
ax' ao = Ale'
A method of generating xi and (Ai, ei) will hereinafter be described
47
CA 02609973 2007-11-28
below.
Subscriber 301 of user apparatus 3 randomly selects tilde xi from
between 0 and 2~ ;L 2, and randomly selects tilde ri from between 0 and n~2.
Then, subscriber 301 calculates:
[Equation 2]
C1 =g lhr
Subscriber 301 generates certifying data indicating that it has correctly
generated tilde xi and tilde ri. Subscriber 301 selects random numbers t1, t2
which satisfy:
[Equation 3]
tl E CO'2A2 I t2 E[O'n2]
and calculates:
[Equation 4]
cl = H(dj hlkt' hr2)
s, = t, - c, x,
s2=t2-c,r
Subscriber 301 sends (C1, c1, s1, s2) to entrustor apparatus 1.
When member registrar 105 of entrustor apparatus 1 has received Cl,
c1, s 1, s2, member registrar 105 confirms whether the equation:
[Equation 5]
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CA 02609973 2007-11-28
CI = " dl' "IIC1 l g Sl ]nS2
is satisfied or not.
If member registrar 105 is able to confirm that the above equation is
satisfied, then member registrar 105 randomly selects a i and a i which
satisfy the condition:
[Equation 6]
lo ai,A G 0,2A2
and sends a i and a i to user apparatus 3.
When subscriber 301 has received a i and 8 i, subscriber 301
calculates:
[Equation 7]
xi = 2A' + (ajzj +,fli mod2" 2 ~
The calculated xi becomes a group signature key.
The group signature key xi is thus randomly generated by entrustor
apparatus 1 and user apparatus 3. However, entrustor apparatus 1 is
unable to calculate a group signature key.
Then, subscriber 301 calculates:
[Equation 81
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CA 02609973 2007-11-28
C2=aXtmodn
Subscriber 301 generates certifying data indicating that it has correctly
generated xi.
Subscriber 301 selects random numbers t3, t4, t5 which satisfy the
condition:
[Equation 9]
t3 E 1jo'11E(1 z+k1 't4 E j0'ljE(22+k)'t5 E iro'lIE(21p2+k)
f
and calculates:
[Equation 10]
C2 OlIhIIdICljlC2lla1IIAIIQt3lIgt3 (g22 )t4 hr5)
S3 = t3 -C2(xi- 221)
S4 = t4 -C2((a+/3_x1 ii +2-1)12"Z )
S5=15-CGI,'jP'
Then, subscriber 301 sends (C2, c2, s3, s4, s5) to entrustor apparatus
1.
When member registrar 105 of entrustor apparatus 1 has received C2,
c2, s3, s4, s5, member registrar 105 checks whether the equation:
[Equation 111
C2 = Wi djhjjdjCjIlC211a]IAll(C2/a2*" )Z as' )c2 g' (g22)S4 hSs
J
CA 02609973 2007-11-28
is satisfied or not.
If member registrar 105 is able to confirm that the above equation is
satisfied, then member registrar 105 randomly selects a prime number ei
which satisfies the condition:
[Equation 12]
el E[2Y' - 2y2 12Y' + 2Y2 ~
and calculates:
[Equation 13]
AI = (C2aoyer mod n
1/ei cannot be calculated unless p' and q' are known.
Member registrar 105 sends the determined (Ai, ei) as a member
certificate to user apparatus 3.
When subscriber 301 of user apparatus 3 has received (Ai, ei),
subscriber 301 checks whether the equation:
[Equation 14]
axia = Ae,
0 a
is satisfied or not to confirm whether the member certificate is correctly
generated or not.
If subscriber 301 confirms that the member certificate is correctly
generated, then subscriber 301 stores the member certificate (Ai, ei) in
51
= CA 02609973 2007-11-28
member certificate memory 302.
Subscriber 301 stores xi as a group signature key in group signature
key memory 303.
Member registrar 105 of entrustor apparatus 1 stores the initially
received private information of user apparatus 3 and the member certificate
(Ai, ei), as related to each other, in member information memory 106.
(Service usage)
It is assumed that outsourcer apparatus 2 provides a music distribution
service to the members of entrustor apparatus 1 and that service revealer
202 of outsourcer apparatus 2 reveals information about music pieces to be
distributed.
Service selector 304 of user apparatus 3 receives a list of distributable
music pieces from service revealer 202 of outsourcer apparatus 2.
It is assumed that service selector 304 has received a list of "music
piece 1, music piece 2, music piece 3, music piece 4, music piece 5".
Based on the user's instruction, service selector 304 selects a music
piece that is to be distributed from the list, and sends the selected music
piece to service revealer 202.
Service revealer 202 sends service information (indicated by m)
corresponding to the selected music piece and additional information to
service selector 304. In the present embodiment, a session ID (indicated by
SID) for managing a session is used as the additional information.
Service selector 304 sends m and SID to group signature generator
305.
Group signature generator 305 calculates group signature data
corresponding to the coupled data of m and SID.
52
' = CA 02609973 2007-11-28
Group signature generator 305 receives a 21p-bit random number w
from random number generator 306.
Group signature generator 305 calculates converted data of (Ai, ei):
[Equation 15]
T, = Aiy'" mod n,T2 = gN' mod n,T3 = ge' h'" modn
based on the random number w, the member certificate (Ai, ei), and the
public information disclosed by public information discloser 102.
Then, group signature generator 305 generates data representing that
it has correctly generated the converted data.
Random number generator 306 generates a random number r1 of f
( y 2 + k) bits, a random number r2 of f(;L 2 + k) bits, a random number r3
of E (;L 1 + 21p +k + 1) bits, and a random number r4 of E (21p + k) bits, and
provides the generated random numbers to group signature generator 305.
When group signature generator 305 has received the random
numbers, group signature generator 305 calculates:
[Equation 16]
2o d, = T,' l(ar2yr')modn,dz = Tz' lgr')modn,d3 = gr~ modn,d4 = gr'hr' modn
Then, using the coupled data of m and SID, group signature generator
305 calculates:
[Equation 17]
c = H(dIhII.vIIaoIIdITIITZjjT3jjdi~jd2~jd3jjd4 IlmlISID)
53
CA 02609973 2007-11-28
Group signature generator 305 calculates:
[Equation 18]
~
s,=Y,-c(e;-2y'),s2=r2-c(x;-2 s3=r3-ceiws4=r4-cw
Group signature generator 305 provides m, SD, and the group
signature data gs = (c, s1, s2, s3, s4, T1, T2, T3) to service requestor 307.
Group signature generator 305 may calculate group signature data
using SID of the coupled data of m and SID, without using m, rather than
calculating group signature data using the coupled data of m and SID.
Service requestor 307 sends the service information m, the additional
information SID, and the group signature data gs to service provider 203 of
outsourcer apparatus 2.
When service provider 203 of outsourcer apparatus 2 has received m,
SID, and gs, service provider 203 sends these items of information to group
signature authenticator 204 in order to authenticate the group signature data
gs.
Group signature authenticator 204 calculates:
[Equation 19]
c'= H(dIhII.vllajjajITjjT2jIT3jlaoTs, -c2'11 / (aS2-cz'~' yS3 )mod nil
T2' -czY' lg~ modnll T2~gs4 mod nIIT2cgs' -~2Y'hs4 modnlln~,SID)
based on the service information m, the additional information SID, the group
signature data gs =(c, s1, s2, s3, s4, T1, T2, T3), and the public information
stored in public information memory 201.
54
CA 02609973 2007-11-28
If the condition that c' = c and s1 is represented by E( y 2 + k) + 1 bits,
s2 by E ( y 2 + k) + 1 bits, s3 by E ( y 1+ 21p + k+ 1) + 1 bits, and s4 by E
(21p + k) + 1 bits is met, then group signature authenticator 204 judges that
the signature is legitimate, and sends the judgment result to service provider
203.
If the condition is not met, then group signature authenticator 204
judges that the signature is illegitimate and sends the judgment result to
service provider 203.
If the judgment result from group signature authenticator 204 indicates
that the signature is legitimate, then service provider 203 distributes the
music piece represented by the service information m to user apparatus 3.
Thereafter, service provider 203 saves the service information m, the
additional information SID, and the group signature data gs = (c, s1, s2, s3,
s4, T1, T2, T3) in service log memory 205.
(User identification)
In the event of a distribution problem, outsource apparatus 2 provides
the service log to entrustor apparatus 1 to ask entrustor apparatus 1 to
identify the user apparatus which has used the service.
Service log provider 206 of outsourcer apparatus 2 sends the service
information m, the additional information SID, and the group signature data
gs = (c, s1, s2, s3, s4, T1, T2, T3), which correspond to the session for
which
the user apparatus is to be identified, from the service log saved in service
log memory 205, to service log receiver 107 of entrustor apparatus 1.
If user apparatus 3 has calculated the group signature data using only
SID of the coupled data of m and SID, then service log provider 206 may
send only SID and the group signature data gs = (c, s1, s2, s3, s4, T1, T2,
CA 02609973 2007-11-28
T3).
Service log receiver 107 of entrustor apparatus 1 sends the received
data to signatory identifier 108.
Signatory identifier 108 confirms an authentication formula:
[Equation 201
c'=x(dIhIIyIIaoIjaIITIITzIIT3jlaoTs,-c2'~] /(asZ-c2~' yS)modnll
T2 cZYl lg~ modnJJT2cg mod nIIT2'gs' -czY'hs' modnll mII SID)
using the public information.
If the group signature data are legitimate, then signatory identifier 108
calculates:
[Equation 211
A' = T/ T2 mod n
using x stored in open key memory 104.
Then, signatory identifier 108 searches the member certificates stored
in member information memory 106 for Ai that agrees with A'.
If signatory identifier 108 finds Ai in agreement with A', then signatory
identifier 108 identifies a user apparatus based on the private information
corresponding to Ai.
[Embodiment 2]
A second embodiment of the present invention will be described below.
The present embodiment corresponds to the second exemplary embodiment
of the present invention.
56
CA 02609973 2007-11-28
In the present embodiment, the key generating process, the key
notifying process, the member registering process, and the service using
process are the same as those according to the first embodiment.
(Charging process)
Entrustor apparatus 1 a receives all the service logs from outsourcer
apparatus 2 and performs a charging process for the use of the service. It is
assumed that a charging method has been determined in advance and
stored in charging information memory 112.
It is assumed that usage frees are defined according to the number of
times the service is used.
Service log provider 206 of outsourcer apparatus 2 sends all the
information (m, SID, (c, s1, s2, s3, s4, T1, T2, T3)) stored in service log
memory 205 to service log receiver 107 of entrustor apparatus 1 a.
When service receiver 107 has received the service log, service
receiver 107 sends the service log to signatory identifier 108.
Signatory identifier 108 confirms an authentication formula of the
information (m, SID, (c, s1, s2, s3, s4, T1, T2, T3)):
[Equation 22]
c'= H(bli""Uyilaollafl'1JITZIIT31laoT]S,-C2Z1 l(QS2~c2"1ys3>modnll
T2'-c2yl lg' modn'lT2cgs
' modn,IT2'g'-c2Y'hs4 modnilmilSID)
using the public information.
If the group signature data are legitimate, then signatory identifier 108
calculates signatory identifying information A':
[Equation 23]
57
CA 02609973 2007-11-28
A'=T/T2 modn
using xi stored in open key memory 104.
Then, signatory identifier 108 searches the member certificates stored
in member information memory 106 for Ai that agrees with A', and identifies
the entity which carries Ai as the user.
If signatory identifier 108 has identified the users of all service logs,
then signatory identifier 108 provides the information (m, SID, and user
names) of all the users to charger 109.
Charger 109 receives the information (m, SID, and user names) and
totals the logs of the respective user names.
Then, based on the number of times that the service is used, charger
109 calculates the usage fees of the respective users according to the
predetermined fee system.
When charger 109 has determined the usage fees, charger 109
notifies the users of the respective usage fees.
[Embodiment 3]
A third embodiment of the present invention will be described below.
The present embodiment corresponds to the third exemplary embodiment of
the present invention.
Entrustor apparatus 1 b has two types of member qualifications, i.e.,
normal membership and special membership.
When user apparatus 3 registers itself as a member in entrustor
apparatus 1, user apparatus 3 selects which membership it wants to be
enrolled with.
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CA 02609973 2007-11-28
(Key generation)
Group key generator 101 of entrustor apparatus 1 generates a key of a
group corresponding to the normal membership.
Specifically, in the same manner as with the first embodiment, group
key generator 101 generates parameters ( E , k, Ip, ;L 1, 12, y 1, y 2),
collision-resistant hash function H, public keys (n, a, a0, g, h, y), member
registration keys (p', q'), and open key x.
Group key generator 101 stores the first public information pkl =(~, k,
Ip, ~, 1, ~. 2, y 1, y 2, H, n, a, a0, g, h, y) in public information
discloser 102,
stores the first member registration keys (p', q') in member registration key
memory 103, and stores the first open key x in open key memory 104.
Second group key generator 111 of entrustor apparatus 1 b generates a
key of a group corresponding to the special membership.
Specifically, in the same manner as with group key generator 101,
second group key generator 111 generates second parameters ( f', k', lp', ;L
~. 1', 12', y 1', y 2'), second collision-resistant hash function H, second
public keys (n', a', a0', g', h', y'), second member registration keys (p",
q"),
and second open key x'.
Second group key generator 111 stores the second public information
pkl =( f', k', lp', ;L 1', ;L 2', y 1', y 2, H', n', a', a0', g', h', y') in
public
information discloser 102, stores the second member registration keys (p",
q") in second member registration key memory 112, and stores the second
open key x in second open key memory 113.
The second parameters and the second collision-resistant hash
function may be of the same values as those of the first public information.
(Key notification)
59
CA 02609973 2007-11-28
Entrustor apparatus lb sends pkl and pk2 to outsourcer apparatus 2a
entrusted with the supply of services. Outsourcer apparatus 2a stores pkl in
public information memory 201 and stores pk2 in second public information
memory 207.
(Member registration)
When user apparatus 3 registers itself as a member in entrustor
apparatus 1 b, user apparatus 3 sends a membership type as well as private
information required for a member registration and a subscription request.
When entrustor apparatus 1 b has received the private information,
entrustor apparatus 1 b determines whether a subscription for user apparatus
3 is permitted or not. If entrustor apparatus lb permits a subscription for
user apparatus 3, then entrustor apparatus 1 b sends information
representing a permission and group information to user apparatus 3.
When a subscription for user apparatus 3 has been permitted,
entrustor apparatus 1 b and user apparatus 3 cooperate with each other in
generating a signature key.
The signature key is generated in the same manner as with the first
embodiment. If user apparatus 3 selects normal membership, then member
registrar 105 of entrustor apparatus 1 uses pkl and (p', q') to generate a
signature key.
If user apparatus 3 selects special membership, then member registrar
105 uses pk2 and (p", q") to generate a signature key.
When user apparatus 3 has selected normal membership, user
apparatus 3 acquires a signature key xi and a member certificate (Ai, ei)
which satisfies:
[Equation 24]
CA 02609973 2007-11-28
ax'a = Ae'
0 i
When user apparatus 3 has selected special membership, user
apparatus 3 acquires a signature key:
[Equation 25]
xi
and also acquires a member certificate:
[Equation 27]
(Ai, ei )
which satisfies:
[Equation 26]
a"'a =Ae'
0 I
User apparatus 3 stores the member certificate in member certificate
memory 302 and stores the group signature key in group signature key
memory 303.
(Service usage)
It is assumed that outsourcer apparatus 2a provides a moving image
distribution service only to special members of entrustor apparatus lb. User
apparatus 3 which have a special member certificate:
[Equation 281
61
' = CA 02609973 2007-11-28
(A1. e1 )
and a group signature key:
[Equation 29]
xi
uses the moving image distribution service of outsourcer apparatus 2a.
User apparatus 3 receives a list of moving images that can be
distributed to special members from service revealer 202 of outsourcer
apparatus 2a.
Based on an operation of the user, service selector 304 selects a
moving image to be distributed from the list, and sends the selected moving
image to service revealer 202 of outsourcer apparatus 2.
Service revealer 202 of outsourcer apparatus 2a sends service
information m corresponding to the selected moving image and additional
information SID to service selector 304 of user apparatus 3.
Service selector 304 sends m and SID to group signature generator
305.
Group signature generator 305 calculates group signature data using
the coupled data of m and SID.
The group signature data are calculated in the same manner as with
the first embodiment, except that the second public information pd2 is used
rather than the public information pdl.
Group signature generator 305 provides m, SID, and the group
62
CA 02609973 2007-11-28
signature data gs2 = (c', s1', s2', s3', s4', T1', T2', T3') to service
requestor
307.
Service requestor 307 sends the service information m, the additional
information SID, the group signature data gs2, and group information V
indicative of the special membership to service provider 203 of outsourcer
apparatus 2.
When service provider 203 of outsourcer apparatus 2has received m,
SID, gs2, and V, service provider 203 sends these items of information to
group signature authenticator 204 in order to authenticate the group
signature data.
When group signature authenticator 204 has received the group
information V, group signature authenticator 204 authenticates the group
signature data using the public information that corresponds to the special
membership indicated by the group information V.
Specifically, group signature authenticator 204 authenticates group
signature data gs2 based on the service information m, the additional
information SID, the group signature data gs2, and the second public
information pk2 stored in second public information memory 207.
The group signature data are authenticated according to the same
authenticating method as with the first embodiment.
Group signature authenticator 204 notifies service provider 203 of
information as to whether the signature is legitimate or not.
If the authentication result from group signature authenticator 204
indicates that the signature is legitimate, then service provider 203 judges
that user apparatus 3 is a special member of entrustor apparatus 1b, and
distributes the moving image represented by the service information m.
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CA 02609973 2007-11-28
Thereafter, service provider 203 saves the service information m, the
additional information SID, the group signature data gs2, and the group
information V, along with time information, in service log memory 205.
(User identification)
Service log provider 206 of outsourcer apparatus 2a sends the service
information m, the additional information SID, the group signature data gs2,
and the group information V, which are saved in service log memory 205, to
service log receiver 107 of entrustor apparatus 1.
Service log receiver 107 sends those data to signatory identifier 108.
When signatory identifier 108 has received the group information V,
signatory identifier 108 confirms an authentication formula for the group
signature data using the second public information pk2 represented by the
group information V.
If the group signature data are legitimate, then signatory identifier 108
calculates signatory identifying information A' i the same manner as with the
first embodiment, using x' stored in second open key memory 113.
Then, signatory identifier 108 searches the member certificates stored
in member information memory 106 for Ai that agrees with A'.
If signatory identifier 108 finds Ai in agreement with A', then signatory
identifier 108 identifies a user apparatus based on the private information
corresponding to Ai.
In the present embodiment, the same group signature scheme is
employed for the normal member group and the special member group.
However, different group signature schemes may be employed.
[Embodiment 4]
A fourth embodiment of the present invention will be described below.
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CA 02609973 2007-11-28
The present embodiment corresponds to the fourth exemplary embodiment
of the present invention.
(Key generation)
As with the first embodiment, group key generator 101 of entrustor
apparatus 1 generates parameters ( E , k, Ip, ;L 1, ~, 2, y 1, y 2), collision-
resistant hash function H, public keys (n, a, aO, g, h, y), member
registration
keys (p', q'), and open key x.
Group key generator 101 stores the first public information pkl =( f, k,
Ip, ;. 1, ;L 2, y 1, y 2, H, n, a, aO, g, h, y) in public information
discloser 102,
stores the first member registration keys (p', q') in member registration key
memory 103, and stores the first open key x in open key memory 104.
The group key generator (not shown) of second entrustor apparatus 4
generates second parameters ( E ', k', Ip', ;, 1', ~, 2', y 1', y 2'), second
collision-resistant hash function H, second public keys (n', a', a0', g', h',
y'),
second member registration keys (p", q2), and second open key x'.
The second group key generator of second entrustor apparatus 4
stores the second public information pk2 = ( E ', k', Ip', ;L 1', 12', y 1', y
2',
H', n', a', aO', g', h', y') in public information discloser 102, stores the
second
member registration keys (p", q") in second member registration key memory
112, and stores the second open key x' in second open key memory 113.
The second parameters and the second collision-resistant hash
function may be of the same values as those of the first public information.
(Key notification)
Entrustor apparatus 1 and second entrustor apparatus 4 sends pkl
and pk2 to outsourcer apparatus 2.
Outsourcer apparatus 2 stores pkl in public information memory 201
CA 02609973 2007-11-28
and stores pk2 in second public information memory 207.
(Member registration)
User apparatus 3 is registered as a member in entrustor apparatus 1
and second user apparatus 5 is registered as a member in second entrustor
apparatus 4 in the same manner as with the first embodiment, using the
public information and the member registration key.
(Service usage)
User apparatus 3 and second user apparatus 5 uses the same in the
same manner as with the first embodiment, using the member certificates
and the group signature keys issued respectively thereto.
However, service requestor 307 of user apparatus 3 sends data G1
indicative of entrustor apparatus 1, in addition to the service information m,
the additional information SID, and the group signature data gs.
The service requestor (not shown) of second user apparatus 5 sends
data G2 indicative of second entrustor apparatus 4, in addition to the service
information m, the additional information SID, and the group signature data
gs.
If the data sent from service provider 203 include the data G1, then
group signature authenticator 204 of outsourcer apparatus 2 authenticates
the group signature data using pkl, and sends the authentication result to
service provider 203.
If the data sent from service provider 203 include the data G2, then
group signature authenticator 204 authenticates the group signature data
using pk2, and sends the authentication result to service provider 203.
After having provided the service, service provider 203 provides the
service log including the data G1 to service log memory 205, and provides
66
CA 02609973 2007-11-28
the service log including the data G2 to service log memory 208.
In the present embodiment, the same group signature scheme is
employed for entrustor apparatus 1 and second entrustor apparatus 4.
However, different group signature schemes may be employed.
In the exemplary embodiments and the embodiments described above,
the illustrated arrangements are shown by way of example only, and the
present invention is not limited to those arrangements.
Industrial applicability:
According to the present invention, when a provider having members is
to entrust a contents provider with the supply of services for the members,
the provider can entrust the contents provider with the supply of the services
without giving member information of the provider to the contents provider.
Therefore, the present invention is applicable to a provider which is to
protect member information and a contents provider which is to reduce the
cost of management of private information.
67
